I found this script the other day, unfortunately I am not sure who the original author was to give credit, but it emails (obviously you want it to go to remote mailserver not on the same machine) you whenever someone logs in. I put this in .bashrc so that anytime someone logs in as me or superuser I get an email. Here's the script as I found it:
echo 'ALERT - Shell Access on:' `date` `who` | mail -s "Alert: (
whatever shell name) Account Access from `who | awk '{print
$6}'`"
PutYourEmail@ADDRESShere
N
ote: If you run SECTOOL it will generate a response from path and alias which will be emailed to you.